This project involves a study of the neuronal and synaptic organization of the mammalian spinal cord and thalamus utilizing light and electron microscopic studies of cat and monkey brain specimens. The normal neuronal constituents are first characterized, and then labeling techniques and utilized to demonstrate particular neuronal systems. egeneration of axons and synapses following experimental lesions provide one labeling method. The other major method used is that of light or electron microscopic autoradiography in which tritiated amino acids are injected into particular regions of the brain and spinal cord, and their transport to synapses and studied by autoradiography. In this way, the precise characteristics of the neuronal circuitry of neuronal groups in the nervous system may be determined. BIBLIOGRAPHIC REFERENCE: Ralston, H.J. III. "The synaptic organization of the monkey spinal cord analyzed by degeneration, autoradiographic, and histochemical techniques". Anat. Rec., 184: 508, 1976.